Many types of gaming and vending machines are activated by the insertion of one or more coins or tokens. Not infrequently, users of these machines will unlawfully insert coins or tokens of a lesser value or even slugs in order to avoid spending genuine coins or tokens. Consequently, the machines are typically equipped with devices which can discriminate between authorized coins and other objects. Such devices generally employ electrical or mechanical sensors which measure the size, weight or magnetic properties of the inserted object. These measurements are the basis upon which the object is either accepted as a valid coin or rejected as a counterfeit.
However, existing coin discriminators, such as those described in the PCT patent application W086/06246 and U.S. Pat. Nos. 3,926,291, 3,998,309, 4,334,604, 4,354,587, 4,359,148, 4,437,478, 4,437,558, 4,469,213, 4,556,140 and 4,662,501, suffer from a number of deficiencies. First, the existing devices tend to improperly accept unauthorized objects because they do not subject the inserted objects to sufficiently rigorous testing. Second, the devices which are most reliable tend to employ costly and complex sensor means. Third, most devices are designed to accept only one type of coin or token and consequently, they may require extensive adjustment or modification when used in a casino which issues a unique type of token or when it is desired to change the coins to be accepted by the machine. Fourth, those devices which can be reprogrammed to accept different coins, for example the system described in U.S. Pat. No. 4,556,140, employ costly and complex technologies and require that the operator insert an inconveniently large number of sample coins to program the device. Fifth, some devices require physical contact between the sensor and the coin, which can cause excessive wear of the sensor.